Raised as the son of a count, he adopted the clerical life following his parents' bitter divorce. For a while, he lived as a Cistercian monk and a hermit, but he and Saint John of Matha came up with the idea of founding an order dedicated to freeing Christian slaves. The Moors in Spain had enslaved many thousands of Christians (estimates vary), and the Arab raiders abducted as many as a 1,250,000 Europeans to sell in the slave markets of the Ottoman Empire. Felix' plan to ransom these slaves would have been debatable today; groups that have tried to purchase intra-African slaves have found that their infusion of western cash incentivizes enslavement. No great surprise to anyone who's thought about economics, but nice folks like Felix think about helping the people who need help, not longterm consequences of such help.
Anyway, if popularity is a measure of success, Felix movement was successful. His Redemptionist Order within the Church was approved in 1198; by 1238, there were 600 houses worldwide. I guess they are better known as the Trinitarians now, though their contemporary work is analogous to their original mission -- they work in prison ministries in over 20 countries.
Tangent: Last spring, I met representatives from Hagar International, a group dedicated to supporting victims of human trafficking in Vietnam, Cambodia, and Afghanistan. Trafficking is probably the most publicized aspect of modern slavery, and anyone who thinks it is not cruelly lethal is deluding himself. If you're curious, check out Hagar International.